Electric-furnace muffle.



J. F. HAMMGND & R. B. SAVIN.- ELECTRIC FURNAGE MUFPLE. APPLICATION FILED PBB.27, 1908.

Patented N ov. 24, 1908.

A .a a "D/Q 4 e E 5' -the county of Richmond,

entren STATES Per 'Naf onere.;

JOHN F. HAMMOND, OF PRINCE BAY, NEW YORK, AND RALPH B. SAVIA", OF PHILADELPHIA,

PENNSYLVANIA, ASSIGNORS TO THE S. S. PENNSYLVANIA.

WHITE DENTAL MFG. CO., OIT PHILADELPHIA.

CTRIC-UBNAGE MUFFLE.

Specication of Letters Patent.

Patented Nov. 24, 1908.

Application lerl February 27, 1908. Serial No. 418,068.

To .all whom 'it mq'y concern.'

Be it known that we, JOHN F. HAMMOND and RALPH B. SAVIN, citizens of the United States, the former residino in4 Prince Bay, in in the State of 'New York, and theI latter residing in Philadelphia,- in the -county of Philadelphia and State of Pennsylvania, have invented certain new and useful Improvements in Electric- Furnace Muiiles; and we do hereby declare .-the following to be a full, clear, and exact description ofthe invention, such 'as will en able others skilled in the art to which it ap pertains to make 'and use the same.

Our invention 4relates to mailles for electric furnaces of the class used by dentists and Y others who require a furnace of small size in which themuflle .is subjected to widely vary mg temperatures ranging from low to ex ceedingly high.' Y

otherwise increase their eiiiciency.

A The invention consists' in the improvements indicated in the accompanying drawings, described in. the following specification and claimed at the conclusion thereof.

In said drawings' Figure lis a perspective View of 'our improved mufile. Fig. 2 is an endwise, vertical sectional view'thereof on the line 2-2 of Fig. 3. Fig. 3 is a crosswise, vertical sectional view on the line 3-3 of F ig. 2. Fig. 4 is a similar sectional view on the line 4 4 of Fig. 2.

The mule consists of an outer member, shell, or dome A and an inner member or amitie proper B, both of which are of rei'ractory material, as tire clay. The dome is hollow and open at. both ends, but at its front end it is of less external diameter, being formed with a liange A. Likewise, the muilie, as the inner member will be herein designated, i3 hollow and open at botli ends, but unlike the dome- `t has no flange at its front end. It is shorter than the dome and wired in the usual manner as indicated by the letter C. The internal diameter of the front end of the dome corres onds to the internal diameter of the mu e; or, in other words, the opening formed by the donnJ flange is of the same size and .shape as the ioterior of the munie, so that the inner Walls of v The object of our invention is to increase with said opening in thev front of the dome. This opening constitutes the vmuflie opening or door through which objects are placed in external diameter of the muille is smaller than the internal diameter of the dome, whereby a space D is formed between the muiile and dome. This space is best filled with a. powdered or granular refractory mate'rial for retainin the vheat in the muflie. For the purpose ofg properly spacing or centering the mutlie in relation to the dome, projections are provided which may either terior of the muilie. The Apreferred form of such projections consists, as shown, of ribs or shoulders a on the .interior of the dome and. extending fromrone` end to the other thereof.' i

A plug of re clay or other suitable material is inserted into the rear of the dome behind the muflle and cemented in place, thisplug serving to close the rear' end of the dome as well as the rear end of .the inutile. This plug may consist of a single piece, or as shown, it may consist of two sections E and E. The section E. rests directly against the rear end of the inutile, while the section E closes the rear end of the dome, the two sections .being spaced from each other, as by lugs e on one or the other of the sections. Tie plug or plugs as the ease may be, correspond in shape but are somewhat smaller than the internal diameter of the dome, and are best formed with lugs e, shown in Fig. 4, adapted to center the plug or plugs. 'the space between the plug sections, if a sectional plug is used, and the space between the plug and the walls of the dome, may be lled with loose refractory material.

As a protection against external injury to the dome and also for holdin it together should it become fractured in use, the sam" may he surrounded by a sheet metal jacket F completely coveringr the top. bottom and sides of the dome, and -fitting ii'. closely, but leaving the e`nds of the dome and the front of the mufiie exposed. Metal Contact posts G anA inserted into ard im.' from the lside of the dome and the oppeite ends of g ehe maffia wire G are passed .through apenthe inutile are flush or substantiaily flushl ings in the side of the dome and through and removed from the mulle chamber, which ,Y is formed by the hollow of the muflie. The

been the interior of the dome or on the ex! openings' or slits in said posts. -The posts serve as contacts for electrically connecting the muifle with the source of electrical supef ply, thus adapting the muliie for use withl a` furnace having spring contacts so constructed that when the mufiie is placed in its support on the furnace, electrical connection is automatically made between the posts of the'mutlle and the spring contacts of the furnace. The metalI jacket F -where the contactposts project from' the dome is formed' withA openings-.fjlarger than said posts in order that the latterwill not come 1n contactvwith. the jacket.

In assembling, the'muflie B is introduced p into the dome A until its front end abuts against the flange A of the dome,the projections. a serving to center the muflle vand, toinsure the interior thereof registering with theffront opening of the dome. Before this is done,'however, the ends of the muflic wire (J are connected to the contact muflle,

. p betwen'the plug sectionsfand'between the plug and dome. To remove the inutile for lrepairingit or for substituting anew one,

the cement whichholds the plug in place is scraped away, the plug orplugs removed and the munie taken out. The chief vadvantage of ou'r im rovedmuflleis that it may be quickly, easi y and ac curatel assembled and taken apart for repair. oreover, it is strong and durable and also of increased .efiiciency The closely v tting metal jacket renders it possible to make the dome of softer material than could otherwise be employed. y v

By using two or more plu s, or plug sections, domes of the same en h may be used with muffles of different engths, the difference being taken up by varying the space between the plug sections or by using more or less plugs.

If the muflie is to be'usedwith a furnace provided with a pyrometer, a thermo-couple H may be carried by the plug -or plugs which close the rear end of the mulile. Here'- in lies another advantage of our invention because the thermo-couple is more easily inserted in and` connected to the plu or' plugs before they are secured to the come than it can be inserted in and connected to the usual solid backs of the muffle and dome.

We claim as our invention 1. An electric furnace mufile comprising 'ii-hollow, electricallywircd inner member, open at both ends, a hollow outer member longer than the inner-member, said outer member beng'open at both ends and formed with `a flange at its front end, anda plug --fitting in the rear end of the outer member for closing 'the rear end of the inner memvberand holding the same in place.

'- 2. .An electric furnace mufile comprising a hollow, electricallyfwired inner member, a hollow outermember longer than the inner member, saidouter member being open at both ends andformed with a flange at its front end,I the internal diameter of the inner member substantially corresponding to the diameter of the opening formed by the flange of the outer member, and a plug fitting in 'the rear of the' outer member for holding the inner member in lace.

-3. An velectric furnace mu le comprising an outer member or dome having a chamber,

-an op'enin in the rear of said member coincident wit the diameter of said chamber, an opening injthe front smaller than the diameter of saidv chamber, a hollow, electricallywired inner member or muflle shorterv than the outer member and located inthe cham'- ber thereof and having an internal diameter substantially equal to the opening in the front of the outer member, and aA plug filling the rear opening of the outer member for holding the inner memberrin lace.

` 4:. vAn electrlc furnace mu e comprising a refractory, hollow, electrically-wired inner member, a refractory, hollow outer member longer than the inner member and the internal diameter of. which is greater than the external diameter of the inner member, said outer member being o en at both ends and having a fiange at its ront end, and a plug fitting in the rear end of the outermember,l

the s ace between the inner and outer me1n bers eing filled with loose refractory material.

hollow, electrically-wired inner. member, av

hollow outer melnber longer than the inner.'

member and the internal 'diameter of which is greater than the external diameter of tie innerv member, said outer member being open at both ends and having a fiange at its front end, and also having internal projections -u on which the inner member rests, and a p ug fitting 'in the rear end of the outer member.

6.- An electric furnace muflie comprising a hollow, electrically-wired inner member, a hollow outer member longer than the inner member. and the internal diameter of which is greater than the external diameter of the inner member, said outer member being open at both ends and having a flange atits front end, and also having an internal projection or projections extending lengthwise ofthe member, the inner member resting upon s ald projection or pro'ectnus, and a plug fitting in the rear en'ilo the outer member.

7. An electric furnace mulle comprising a hollow, electrically-wired inner member, a hollow outer member longer than the inner member and the internal diameter of which is greater than tlre external diameter of the inner member, said outer member beingopen at bothends and having a flange at its front end, and also having a central bottom projection and side projections, the inner member resting upon said projections, and a plug fitting in the rear end of the outer member.

8. An electric furnace mufile comprising a hollow, electrically-wired inner member open at both ends, a hollow outer member longer than the inner member, said outer member being open at both ends and having a flange at its front end against which the inner member abuts, a plugin the rear of the outer member abutting against and closing the rear end ofthe inner member, and another plug closing the rear end of the outer membr and spaced from the first mentioned uO. p 9? An electric furnace mufiie comprising a hollow, refractory, electrically-wired inner member open at both ends, a hollow refractory outer member longer than the inner member and the internal diameter of'which is greater than the external diameter of the inner member, said .outer member being open at both ends and having a flange at its front end against which the inner member abuts, a plug in the rear of the outer member abutting against and closing the rear end of the inner member, another plug closing the rear 'end of the outer member and spacedfrom the first mentioned plug, and loose refractory material filling the space between the inner member, and contact posts inserted in and projecting from the vexterior of said outer member, the opposite ends of the mufiie wire being connected to these posts.

l2. An electric furnace mufiie comprising a hollow,"electrically wired inner member open at both ends, a hollow outer member longer than the inner member, said outer member being open at both ends and formed with a flange at its front end, and a plug or plugs fitting in the rear. end of the outer member for closing the rear end of the inner member and holding the same in place, a thermocouple passing through and being connected to said plug orplu s.

In testimony whereof we a x our signatures in presence of two witnesses.

JOHN F. HAMMOND RALPH B. sAviN. 

